#include<list>
#include<iostream>
using namespace std;
int main()
{
	list<int>monkeys;
	int n,m;
	while(true){
		cin>>n>>m;
		if(n==0&m==0)
		break;
		monkeys.clear();
		for(int i=1;i<=n;i++)
		monkeys.push_back(i);
		list<int>::iterator it=monkeys.begin();
		while(monkeys.size()>1){
			for(int i=1;i<m;++i){
				++it;
				if(it==monkeys.end())
				it=monkeys.begin();
			}
			it=monkeys.erase(it);
			if(it==monkeys.end())
				it=monkeys.begin();
		}
		cout<<monkeys.front()<<endl;
		}
			return 0;
}
